From your waistline to your heart, we took a closer look at what's going on in your body when you don't get your fiber fill.

Vanessa Rissetto M.S., R.D., C.D.N.
October 29, 2020
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Fiber may not be the sexiest nutrient to talk about, but it's one of the best things you can eat for your health. Dietary fiber is a type of carbohydrate that is resistant to digestion and absorption by humans. Fiber is found in fruits, vegetables, whole grains, beans, legumes, nuts and seeds (try these healthy high-fiber foods to get your fill). There are two main types of fiber—soluble and insoluble and each type has its own benefits for human health. Epidemiological research has consistently shown that people who eat high-fiber diets have a lower risk for cardiovascular disease, cancer, type 2 diabetes and obesity. We all know that fiber is good for us, but only about 5% of Americans meet the recommendations for daily fiber intake.

But what exactly happens in your body when you consistently don't get enough fiber? We dug into the science to find out about six things that can happen when you don't eat enough fiber.

1. You have a higher risk of cardiovascular disease

Cardiovascular disease is the leading cause of death for adult men and women in the United States, leading to over 650,000 Americans deaths every year. Scientists have identified key nutrition and lifestyle factors that help prevent heart disease, and eating a high-fiber diet is at the top of the list.

Results from a large meta-analysis published in the BMJ found that every 7 additional grams of daily fiber led to a 9% reduced risk of CVD. More evidence from another meta-analysis with over 650,000 participants showed that people with the highest intake of both soluble and insoluble fiber had the lowest risk of coronary heart disease. Keep your heart healthy by adding high-fiber foods like oatmeal, berries and nuts to your diet (eat more of these top 15 heart-healthy foods too).

2. You might not live as long

Another big benefit of eating more fiber: It helps you live longer even if you don't have cardiovascular disease. According to a large body of observational research, people who eat more fiber have a lower risk of all-cause mortality compared to people who don't eat enough fiber.

While these stats are a little scary, there's some good news: eating 10 additional grams of fiber per day can help decrease your risk of early death by 10%! That's the equivalent of adding one sweet potato and a 1/2 cup of chickpeas to your day. Our cherry smoothie (pictured above) has 6 grams of fiber.

3. You may have increased inflammation in your body

Chronic inflammation is a major risk factor for several diseases, including cardiovascular disease, type 2 diabetes and cancer. Diet and lifestyle factors like stress, smoking and—you guessed it—not eating enough fiber can increase inflammation and make us more susceptible to chronic disease. (Try eating more of these top inflammation-fighting foods.)

We still need more research to understand the benefits of fiber for inflammation, but observational studies have shown that high-fiber diets are associated with decreased markers of inflammation. Some clinical trials have also found that increasing fiber, modifying fat intake and losing weight significantly lowered markers of inflammation in study participants.

4. Your immune system won't be as strong

Studies have also shown that dietary fiber may help fight inflammation by fueling the beneficial bacteria in your gut that support your gastrointestinal immune system, known as gut-associated lymphoid tissues or GALT. Strengthening the immune system in your gut is also important for supporting your overall immune health and fighting infections. We often hear about eating probiotics, beneficial bacteria found in yogurt, kimchi and kefir, for a healthy gut. But eating more fiber is important too. Eating prebiotics, a healthy fiber found in wheat, walnuts, bananas, legumes and more, helps keep your gut healthy. Other research has linked soluble fiber intake with a stronger immune system.

5. It's harder to manage your weight

Losing weight and keeping it off is hard—not eating enough fiber makes it even harder.

Eating more fiber is a helpful tool for weight loss because it helps you feel full and satisfied after eating. Dietary fiber slows down digestion and absorption of food, giving your gut enough time to communicate with your brain that you are full and it's time to stop eating.

Fiber also helps balance our blood sugar and insulin response, which helps stabilize our appetite and promote fat burning instead of fat storage.

Another win for weight management: fiber has zero calories. Since fiber is a nondigestible carbohydrate, we can't metabolize it for fuel. Fiber also binds to fats and other sources of calories from food, decreasing your overall calorie intake from other macronutrients.

Still not convinced that fiber is a weight-loss superfood? Epidemiological evidence shows that high-fiber diets are associated with a lower body weight and less body fat. So if you want to lose weight and keep it off, eat more fiber.

6. You're going to the bathroom too much, or not enough

If you want a healthy digestive system, adding more fiber to your diet will do the trick.

Millions of people around the world suffer from irritable bowel syndrome, a condition that causes uncomfortable symptoms like constipation, diarrhea and bloating.

While the causes of IBS are not entirely known, eating more dietary fiber has been identified as an effective treatment for the disease. Fiber has a unique ability to both slow gastrointestinal transit time (which helps treat diarrhea) and stimulate gastrointestinal motility (which helps treat constipation).

Eating more fiber also helps strengthen the lining of your colon, which researchers think might be why high-fiber diets are associated with lower colon cancer risk. High-fiber diets may also lower your risk of hemorrhoids, diverticular disease and inflammatory bowel disease.